<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    </head>
    <body>
        <script>
            let arr = [1, 2, 3, 1, 2, 4, 5];
            let value = arr.reduce((pre, cur) => {
                cur in pre ? pre[cur]++ : (pre[cur] = 1);
                return pre;
            }, {});
            console.log(value);
        </script>
    </body>
</html>
